You can't do it in this game. Mainly due to the order filling feature, and due to everyone being able to automatically undercut the lowest seller in the UI. Add in the fact that listing prices (and sales tax) add up to 15%, and it's even more impossible.
Do researchs on items with a high discrepancy between orders and sells or between an item before and after you mess with it via crafting, salvaging, etc.
The max I've found till now only nets me 1g every 15 items, or so, bought and sold though :/